1630.7 
Uc-179 
c  .3 


11-4-051  Of 

MAY  1932 

DOCS 


UNIVERSITY  OF  ILLINOIS 

Agricultural  Experiment  Station 

URBANA,  ILLINOIS,  APRIL,  1915 


CIRCULAR  No.  179 


FOUR  APHIDS  INJURIOUS  TO  THE  APPLE 

By  B.  S.  Pickett 
Assistant  Chief  in  Pomology 

Aphids  infesting  the  apple  buds  appeared  in  serious  numbers 
during  the  present  season  (1915)  in  the  University  orchards,  when  the 
buds  began  to  swell.  They  were  also  observed  in  neighboring  orchards 
and  in  the  experimental  orchards  of  the  Department  at  Olney  and 
Neoga.  In  1914,  apple  aphids  caused  serious  damage  in  certain  coun¬ 
ties  in  Illinois,  and  some  damage  was  reported  from  many  sections  of 
the  state.  With  a  view  to  finding  the  extent  of  the  present  season's 
infestation,  the  writer  telegraphed  to  six  orchardists  in  representative 
parts  of  the  state  for  information  as  to  the  occurrence  of  the  insects. 
The  replies  were  as  follows : 

From  Johnson  county. — Aphis  worse  than  ever  before.  Something  must 
be  done  quickly  or  crop  is  ruined. 

From  Marion  county. — Aphis  situation  much  more  serious  this  morning 

(April  10). 

From  Union  county. — Find  some  aphis  but  not  in  alarming  numbers. 

From  Washington  county. — Do  not  find  any  aphis. 

From  Jersey  county. — Green  aphis  very  bad  on  almost  all  orchards. 

From  Tazewell  and  McLean  counties. — The  aphids  are  very  bad  at  Lilly. 
At  Normal  there  are  some  aphids  on  some  trees. 

The  replies  indicate  a  serious  infestation  more  or  less  widely 
spread  over  the  state,  and  the  Department  of  Horticulture  is  therefore 
preparing  this  brief  circular  in  order  to  provide  information  regarding 
the  insects  and  to  suggest  measures  for  their  control. 

Character  of  Injury 

The  aphids  attack  the  opening  buds,  the  young  fruits,  the  growing 
shoots,  and  the  leaves,  sucking  the  plant  juices  from  the  succulent  parts 


by  means  of  long,  very  slender,  tube-like  beaks  which  they  thrust  thru 
the  skins  of  the  affected  organs  into  the  soft  tissues  beneath.  They 
weaken  the  blossom  buds  by  removing  the  sap ;  they  dwarf  and  de¬ 
form  the  apples  so  that  varieties  of  ordinary  size  frequently  fail  to 
grow  larger  than  small  crab  apples,  and  the  fruits  have  a  puckered 
appearance  about  the  calyx  end;  they  suck  the  juice  from  the  growing 
shoots,  dwarfing  them;  and  they  cause  the  leaves  to  curl,  and  if  the 
insects  are  present  in  large  numbers,  to  dry  up  and  fall  off.  They  are 
more  injurious  to  the  growth  of  young  trees  than  of  old  trees.  In  old 
trees  their  chief  injuries  are  on  the  fruit. 

Description  of  the  Aphids 

Four  kinds  of  aphids  attack  the  apple,  the  Apple  Aphis  ( Aphis 
pomi  DeG.),  the  Rosy  Apple  Aphis  ( Aphis  sorbi  Kahl.),  the  European 
Grain  Aphis  ( Sipliocoryne  avenac  Fab.),  and  the  Clover  Aphis  ( Aphis 
bakeri  Cowen).  All  kinds  are  small,  soft-bodied,  sucking  insects  re¬ 
producing  themselves  with  great  rapidity  in  dry,  warm  weather.  Cold, 
heavy  rains  are  detrimental  to  the  propagation  and  development  of 
the  insects.  The  various  species  differ,  however,  in  their  appearance 
and  habits  in  some  important  respects. 

The  Apple  Aphis  eggs  are  deposited  in  the  fall  on  the  new  shoots 
and  at  the  base  of  the  bud  scales.  The  eggs  are  small  shining  black 
objects  and  are  often  to  be  found  in  great  numbers.  The  eggs  hatch 
about  the  time  the  buds  begin  to  open,  and  the  aphids  may  be  found 
infesting  the  young  shoots,  expanding  leaves,  and  flower  buds.  The 
adults  are  one-twelfth  of  an  inch  long,  and  bright  green  in  color.  This 
species  is  particularly  partial  to  the  young  shoots  and  tender  terminal 
leaves,  but  it  also  deforms  and  stunts  the  fruit  when  present  in  large 
numbers  during  and  immediately  following  the  blooming  period.  The 
Apple  Aphis  lives  on  the  apple  trees  thruout  the  year. 

The  Rosy  Apple  Aphis  eggs  are  deposited  in  the  same  manner  as 
those  of  the  Apple  Aphis  and  hatch  at  the  same  time  in  the  spring. 
The  adults  are  slightly  larger  than  those  of  the  Apple  Aphis,  one- 
tenth  of  an  inch  long,  and  are  variable  in  color,  usually  rosy,  but  some¬ 
times  gray,  purplish,  or  black.  This  species  is  particularly  partial  to 
the  fruit  spurs  and  destructive  to  young  fruits,  tho  it  also  attacks  the 
young  shoots  and  causes  the  leaves  to  curl  as  does  the  Apple  Aphis. 
Unlike  the  Apple  Aphis,  this  species,  after  producing  three  generations 
on  the  apple,  migrates  to  some  unknown  food  plant,  where  it  passes 
the  summer,  returning  to  the  apple  trees  in  the  fall. 

The  European  Grain  Aphis  lays  its  eggs  on  the  apple  in  the  fall 
and  produces  two  generations  on  the  apple  in  the  spring,  after  which 
it  migrates  to  grass  and  grain  crops  for  the  summer,  returning  to  the 
apple  in  the  fall.  The  adults  are  smaller  than  the  previous  species  and 
green  in  color.  It  infests  the  flower  buds  and  blossoms  to  an  even 
greater  extent  than  the  Apple  Aphis  or  the  Rosy  Apple  Aphis,  butr 


i 


3 

owing  to  its  earlier  migration,  it  is  less  injurious  to  the  leaves  'and 
young  shoots. 

The  Clover  Aphis  lays  its  eggs  in  the  fall  on  the  shoots  of  the 
apple.  The  eggs  hatch  a  week  or  more  before  the  Apple  Aphis.  Most 
of  the  aphids  migrate  to  clover  or  alfalfa  in  June,  tho  a  few  appear 
to  remain  on  the  apple  thruout  the  season.  The  adults  are  light  yellow 
or  pink  in  color. 

All  the  species  described  occur  in  Illinois,  and  more  than  one  of 
them  may  be  found  the  same  season  in  the  same  orchard.  In  fact  it 
is  quite  possible  that  all  four  species  are  sometimes  present  in  the  same 
orchard.  Information  as  to  the  relative  seriousness  of  the  different 
species  is,  unfortunately,  incomplete ;  orchardists  are  advised  to  observe 
carefully  the  habits  and  appearance  of  these  insects  as  thev  have  op¬ 
portunity  in  their  orchards,  in  order  to  identify  the  species  and  to 
determine  whether  or  not  the  particular  species  present  is  causing  suf¬ 
ficient  injury  to  call  for  remedial  measures.  During  the  present  season 
orchardists  should  make  an  immediate  examination  of  their  trees  and 
if  aphids  are  found  in  large  numbers,  should  take  immediate  steps  to 
combat  them.  Growers  whose  orchards  suffered  in  1914  should  be 
especially  prepared  to  fight  these  pests  this  spring. 

Remedial  Measures 

The  species  of  aphids  above  described  are  easily  killed  in  the  adult 
stage  by  certain  contact  sprays.  Winter  applications  of  lime  sulfur 
cannot  be  depended  on  to  destroy  the  eggs.  Poison  sprays  such  as 
ai  senate  of  lead  are  not  eaten  by  this  type  of  insect,*  and  consequently 
are  ineffective  remedies  for  aphids.  Kerosene  emulsion  is  effective 
but  is  uncertain  in  its  effect  on  the  foliage  of  the  trees.  The  best  avail¬ 
able  sprays  are  the  tobacco  decoctions,  of  which  the  one  most  widely 
m  use  is  '‘Black  Leaf  40,”  a  proprietary  tobacco  extract,  made  by  the 
Kentucky  Tobacco  Products  Company,  Louisville,  Kentucky.  'This 
mateiial  is  used  at  the  rate  of  one  gallon  in  one  thousand  gallons  of 
spray.  It  may  be  combined  with  lime  sulfur,  lime  sulfur  arsenate  of 

lead,  Bordeaux,  or  Bordeaux  arsenate  of  lead,  not  with  arsenate  of  lead 
alone. 

The  ideal  time  to  spray  for  these  aphids  is  just  as  soon  as  all  or 
nearly  all  the  eggs  appear  to  have  hatched.  Observations  made  in  the 
Lniveisity  orchards  this  season  indicate  that  all  the  eggs  hatched  before 
the  blossom  buds  began  to  separate.  After  the  leaves  expand  some¬ 
what  and  the  blossom  buds  separate,  the  aphids  are  provided  with  more 
hiding  places  and  are  more  difficult  to  hit  with  the  spray.  Unfortu¬ 
nately,  spraying  at  this  time  would  require  an  extra  application  in 
addition  to  the  cluster  bud  spray  (made  for  scab,  curculio,  bud  moth, 
spring  canker-worms,  etc.),  and  would  thus  add  seriously  to  the  cost 
of  the  season’s  operations.  Spraying  for  aphids  at  the  time  of  the 
cluster  bud  spray  is,  however,  highly  effective,  and  in  general  it  is 


UNIVERSITY  OF  ILLINOIS-URBAN  A 


3  0112 121972209 

• 

advised  that  this  method  be  followed.  If,  however,  previous  experi¬ 
ence  has  shown  serious  losses  from  aphids,  or  if  they  are  present  in 
extremely  large  numbers,  the  extra  application  may  be  well  worth 
while. 

Fruit  growers  will  confer  a  favor  on  the  Department  of  Horticul¬ 
ture  if  they  will  write  us  the  results  of  their  observations  on  the 
behavior  of  the  aphids  during  the  present  season.  The  points  on 
which  information  is  particularly  desired  are  the  time  of  appearance 
and  extent  of  the  infestation,  the  color  of  the  adults,  the  duration  of 
the  attack,  the  disappearance  and  reappearance  of  the  aphids,  if  these 
occur,  and  the  success  or  failure  of  any  remedial  measures  tried.  Such 
information  will  be  very  helpful  in  determining  the  extent  of  the  need 
for  treatments  and  the  character  of  the  treatments  themselves. 


